In spectral photon-counting computed tomography (CT) small pixels of a dedicated spectral detector are used for determining energy of localized photon-to-electron conversions in a so-called direct conversion layer. State-of-the-art direct conversion layers in spectral detectors are usually based on cadmium zinc telluride (CZT) or cadmium telluride (CdTe) technologies and are typically greater than 1.5 mm thick for high photo-peak absorption and system sensitivity. Irradiation rates in a direct beam area are of an order of up to 10{circumflex over ( )}9 x-ray photons per square millimeter and second. Pixels should therefore be well below square millimeter size to allow single photon counting with readout times in the range of tens of nanoseconds. State-of-the-art CZT technology, using horizontal slabs of CZT with pixelated top or bottom contacts, allows for a typical minimum pixel size of 0.2-0.5 millimeters for a 2 millimeter detector thickness. This is not sufficient for high irradiation rates since state-of-the-art photon counting electronics cannot support the rate/channel equivalent in air. An alternative solution is to illuminate the CZT edge on. However, this requires very thin slabs of CZT, typically below 1 millimeter, which is very difficult to handle and manufacture in homogenous high quality that is required, making it a costly process. On top of that CZT itself is an expensive material.